<!DOCTYPE html>
<head>
  <title>Example</title>
</head>
<body>
  <!-- An image should be annotated. -->
  <div>
    <img src="red.png" width=16 height=16>
  </div>

  <!-- An image in an anonymous iframe should be annotated. -->
  <iframe></iframe>

  <script>
    let iframe = document.querySelector('iframe');
    iframe.contentDocument.body.innerHTML = `
      <img src="green.png" width=16 height=16>
    `;
  </script>
</body>
